Almost always use this as the left hand side of a WhenAny call.

Do

public class MyViewModel
{
  public MyViewModel(IDependency dependency)
  {
    Ensure.ArgumentNotNull(dependency, "dependency");

    this.Dependency = dependency;

    this.stuff = this.WhenAny(x => x.Dependency.Stuff, x => x.Value)
      .ToProperty(this, x => x.Stuff);
  }

  public IDependency Dependency { get; private set; }

  readonly ObservableAsPropertyHelper<IStuff> stuff;
  public IStuff Stuff
  {
    get { return this.stuff.Value; }
  }
}

Don't

public class MyViewModel(IDependency dependency)
{
  stuff = dependency.WhenAny(x => x.Stuff, x => x.Value)
    .ToProperty(this, x => x.Stuff);
}

Why?

• The lifetime of dependency is unknown - if it is a singleton it could introduce memory leaks into your application.